This proposes to etablish and operate a clinical unit in the NCI's multicenter randomized clinical trial of the efficacy of a diet low in fat (20% of calories) in the treatment of women with Stage II breast cancer. The trial's primary objective is to determine if the low-fat diet can decrease the incidence of recurrence of breast cancer. The secondary objective is to determine if the diet will decrease the incidence of second primary tumors. This application proposes the unit's participation in all three phases of the trial by the cooperative agreement mechanism; development of the protocol in two months, the feasibility trial of ten months, and the full-scale trial of 48 months. For the feasibility and full-scale trials, the unit will study two cohorts of 66 patients recruited by the Baylor Oncology Service at the Methodist Hospital, according to the protocol's criteria. The unit will collaborate with the trial's other clinical units, nutrition coordinating unit, statistical coordinating unit, and the NCI. The Baylor unit's major aims include: 1) To operate the clinic unit with economy and accuracy using a microcomputer assisted surveillance and management of clinic operations, and collection and quality control of data. 2) To gain maximum dietary adherence for this efficacy trial using a combination of standard and innovative techniques, including selection of subjects with high potential for adherence by an adherence screening examination and washout criteria, individual counseling by experienced dietitian/adherence counselers trained in counseling techniques developed by the Baylor Lipid Research Clinic aided by the 'instant' analysis of the patient's 7-day food record by the microcomputer based Nutrient Analysis System, and multimedia instruction by food models, cooking demonstrations, slide tapes, newsletters, and bulleting boards. Adherence counseling is based on the identification, diagnosis of and management of adherence problems using behavioral techniques and frequent counselor-patient contact. 3) To evaluate methods of diet recording, 24-hour diet recall, 1-7 day diet self-recording, and objective measures of diet adherence, body weight, skin-fold thickness, plasma total cholesterol, and HDL-cholesterol, and the proportion of lineleic acid in the plasma cholesterol esters. The optimum methods of clinical trial operation, adherence management and surveillance, from the feasibility trial will be applied to the full-scale trial. The project's significance is its potential for developing a dietary treatment and preventive procedure for Stage II breast cancer.